IS-1: Goals of IS-1 are to determine the extent to which frail, old men (n=80) and women (n=80) can respond to 9 months of exercise training with the cardiovascular, musculoskeletal, and central nervous system adaptations that have been shown to occur in younger people. If such adaptations occur, an additional aim is to determine if the magnetude of the improvements is sufficiently large and functionally important to result in improvements in performance of activities of daily living. IS-2: Goals of IS-2 are to determine if hormone replacement therapy (HRT) can reduce fraility in old women (n=120) with physical frailty, and to determine if 9 months of exercise training brings about greater improvement s in old women who have been on HRT for 9 months than in sex hormone deficient women.